One previously known way for securing an engine to a vehicle frame, while providing decreased transmission of noise and vibration and restraint of engine torque reactions, is to utilize a torque strut with hydraulic piston action to dampen the engine torque reactions. The torque strut is pivotally attached to the engine axially in the direction of greatest torque reaction, with the opposite end pivotally attached to the vehicle frame, and with flow control means in the strut to regulate transfer of hydraulic fluids to either side of the piston as the strut is subjected to engine torque loads. An apparatus for resisting engine torque reactions is disclosed in U.S. Pat. No. 4,518,058.
U.S. Pat. No. 4,706,946 discloses a mechanical connecting link or strut that accommodates limited motion due to normal engine oscillations and restrains excessive engine motion as results from engine torque. The dampening is achieved through a mechanical apparatus utilizing sliding plates and friction elements which are compressed between the plates.
U.S. Pat. No. 4,779,834 discloses an alternative way of providing a torque strut arrangement to limit engine roll, while providing dampening of vibration. This engine displacement limiter utilizes a three-point torque strut to resist the rolling action of an engine from reactive torque thereon, and utilizes rubber bushings at the three attachment points to provide isolation of the engine to frame.
Although these torque-resisting struts are able to provide isolation of small displacement vibrations between the engine and the vehicle frame, and resistance of large displacement engine torque to prevent large rotational displacement of the engine, especially under rapid throttling and acceleration of the engine and vehicle, they also possess a number of significant disadvantages and require many subassembly components in their construction. Over extended periods of use, the components wear and age as both the hydraulic piston strut and rigid strut with rubber bushings are subjected to vibration and thermal cyclic loading. In use, the tearing of rubber bushings on rigid engine struts is a problem that is difficult to prevent. As with any complex mechanical apparatus, the hydraulic piston strut utilizes many mechanical components with interacting frictional interfaces, thereby leading to wear of individual components and eventual leakage of hydraulic fluid. Likewise, the torque-resisting strut utilizes a complimentary pair of elongate slidable plates with frictional elements which will be subjected to the long term effects of component wear.